what do you mean non-performance? in studies?
Thats just one aspect of schooling.. so are you saying your teen is not studying or that he is studying and still not doing well? or what?
if your child is not liking to study, then you can make him enjoy it in a different more practical way..make him actually do experiments at home.. make him use his studies in his day to day life.. which subjects is he/she not doing well in?